The invention relates, primarily, to the repair of peripheral nerves which have been severed through accident or, perhaps, required medical procedure. Peripheral nerve fibers which have been severed may, under some circumstances, regenerate if proper steps are taken to promote such regeneration. In the past, several techniques have been utilized to attach and promote nerve regeneration.
In cases where the gap between proximal and distal ends of the severed nerve has been small enough, a technique of suturing the two ends together has been used in order to promote regeneration of nerve fibers across the gap. Notably, this technique cannot be used in applications where the gap is greater than one centimeter. This method of bridging often proves unsatisfactory because the suturing process can damage both the nerve fibers and the epineurium, and the sutures may produce excessive foreign body reactions. Additionally, the surgical manipulations required to effectuate the repair may induce the formation of excessive scar tissue which frequently interferes with growth of the proximal stump axons into the distal nerve stump.
In cases where the gap between the proximal and distal ends of the severed nerve cell has been too great to suture the two ends together, a method of spanning the gap has been used. In one application, a graft of autologous sural or other nerve tissue has been taken from elsewhere in the body to serve as the bridge between the severed ends. This method has the unfortunate effect of sacrificing normal nerve tissue from the donor area. Many procedures of bridging the gap have been tried in the past making use of synthetic materials such as tantalum, cellulose polymer, and silicone, but these materials have caused a capsule to form and, in some cases, fibrosis or calcification. Additionally, silicone nerve repair devices have been shown to require careful matching of the tube size to the size of the nerve being repaired. Silastic.RTM. tubes are also reported to result in nerve fiber damage which has resulted over time because of the non-bioresorbable nature of the material.
Antigenic and other reactions which are experienced with use of synthetic materials have been avoided through use of biopolymers which are biodegradable within the body. Many biopolymers have been tested including a fibrinogen and fibrin mixture, and collagen. However, these materials have also proven unsatisfactory because of inadequate vascularazation, adverse tissue reactions, fragmentation of the material, or excessive persistence in the body.
The invention disclosed herein is a biodegradable tubulization material comprised of fibrin and collagen layers which effectively overcomes the problems experienced with other techniques and materials used for repairing nerves.